This application claims the benefit of Japanese Patent Application No. 2006-052441, filed Feb. 28, 2006, which is incorporated herein by reference.
1. Field of the Invention
Embodiments of the present invention relate to an ink-jet recording apparatus that includes a mechanism that optically detects an amount of liquid remaining in a liquid chamber of a cartridge.
2. Description of the Related Art
An ink-jet recording apparatus includes an ink cartridge that supplies an ink to an ink-jet head. The ink cartridge may be attached to or detached from the ink-jet recording apparatus. When the ink chamber of the ink cartridge is empty, if the ink-jet head attempts to eject ink, not only will no ink be ejected, but also air may pass into the ink-jet head, for example as an air bubble. Therefore, it is useful to detect the amount of ink that remains in the ink chamber of the ink cartridge.
In one method of detecting remaining ink, the amount of ink used in printing is estimated, and the remaining amount of ink is determined. However, there may be error in this estimate. As a result, an ink cartridge may no longer be used even though some ink remains in the ink cartridge, which wastes the ink. For errors in the other direction, there may not be any ink remaining in the ink chamber and thus air may enter the ink-jet head.
To avoid this problem, a technology that uses the float has been suggested (for example, Japanese Patent Publication No. H09-001819 A). According to this technology, a non-light transmitting float that has a smaller specific gravity than an ink is disposed on the ink that is stored in an ink chamber of an ink cartridge. The float then floats on the ink and descends as the liquid surface descends with the use of ink. An optical path, which passes from a light emitting unit to a light receiving unit in an optical sensor disposed outside the ink, is interrupted by the float or other components of a float assembly when there is too little ink in the ink chamber. To use this technology, the light must be able to pass through the ink so that movement of the float into the light path is detectable. Accordingly, the ink in the ink chamber should allow high levels of light transmission. Typically to achieve this property the ink must contain a dye. Inks containing substantial amounts of pigment typically are not sufficiently light-transmissive to allow light from the light emitting unit to pass through the ink to the light receiving unit. As a result, the optical detector cannot distinguish the ink from the float.
Dye-based ink has a disadvantage in that it is likely to bleed on recording paper. In particular, when a character is recorded, the contour thereof easily becomes faint. To perform high quality ink-jet printing, a non-light transmitting pigment black ink is generally used as a black ink when the character is recorded in particular.
Pigment-based ink, in contrast, does not transmit light, making it difficult or impossible to distinguish from a float using an optical sensor. As a result, one cannot accurately detect the amount of pigment-based ink remaining in an ink chamber using a float and an optical sensor.
One may, however, detect pigment-based ink directly, without the need for a float, using an optical sensor because the ink itself interrupts the optical path. When highly accurate detection is performed by using this sensor, or when an optical sensor with low sensitivity is used to reduce cost, the ink chamber contains a narrow region to decrease the thickness of the ink layer between the light emitting unit and the light receiving unit of the optical sensor. However, ink in the narrow region adheres to the surface of the inner walls of the ink chamber by surface tension and rises. The causes the edges of the ink along the walls to be higher than the actual ink liquid surface. As a result, of the optical sensor detects an amount of ink remaining in the ink chamber that is larger than an actual amount. This problem occurs in not only ink containing the pigment but also ink containing the dye and ink-jet liquids (the fixing liquid, the colorless transparent ink, the shipping liquid and the like).